The precise alignment of optical components is essential to efficient operation of optical devices, such as lasers and equipment utilising lasers. Typical optical alignment devices are translation and rotation stages that are bolted together to give the desired degrees of freedom for adjustment of each optical element. Maintaining accurate alignment of every component can be difficult, especially if thermal changes occur. Careful adjustment of optical mounts is a skill developed early by optical engineers and scientists.
One type of mount providing rotational adjustment on two axes is a kinematic mount. An example of a kinematic mount is found in U.S. Pat. No. 4,088,396 assigned to Ardel Kinamatic. The Ardel Kinamatic mount provides for orthogonal adjustment on two axes which pass through the geometric centre of the optical component held in the mount.
U.S. Pat. No. 6,198,580 assigned to Newport Corporation also describes a kinematic mount but one which pivots about the surface of the optical element so as to avoid introducing phase shifts. Although easy to use the mount is designed as a laboratory device that will require frequent adjustment.
Frequent minor adjustment of optical alignment is not possible for commercial products. For example, laser systems are finding application in many different areas of medicine, including ophthalmology and surgery. The medical practitioner does not have the skill or the desire to make continual minor adjustments to optical alignment in order to maintain peak performance of laser equipment. For this reason it has been necessary to design optical mounts that can be set and locked in place. In addition, devices have become ever more compact and low cost thus adding the complication of requiring compact mounts which do not require adjustment after they are set, have thermal stability, and are low cost.
Thermal stability can be a critical issue for some laser related optical components and alignment devices. Optical components, such as non-linear crystals, that absorb a small percentage of the laser beam passing through it and convert it to heat, must be kept at a stable temperature to maintain optimal performance, and the heat from the optical component must not cause mechanical alignment changes. A temperature control device may be required between the optical component and the mount.
Another important consideration is that any angular rotation of the optical component is carried out around the geometric centre point. If this cannot be achieved any angular adjustment may require a compensating lateral adjustment to ensure that the beam is entering and exiting the optical component correctly. For most laser applications only a relatively small range of angular adjustment range is required, however fine adjustment over that range is required, which can then be locked without changing the alignment.
These demanding design requirements for a gimbal mount including; fine, precise and lockable angular adjustment about the geometric centre of the optical component in two planes, the ability to maintain temperature stability of the optical component, the ability to fit a temperature control device, small size, and low cost are not achieved in previous designs.